1. Technical Field of the Invention
The present invention relates to a vehicle headlamp having a discharge bulb, and more particularly to the configuration of the lens of the vehicle headlamp.
2. Related Art
Recently, a discharge bulb has been employed as a light source for a vehicle headlamp because it irradiates with high luminance. The discharge bulb is much higher in power than a halogen lamp or the like. Therefore, it is desirable that a headlamp with a discharge bulb performs the function of a discharge bulb sufficiently--for instance, its irradiation angle is set large.
In general, a pair of headlamps are provided on the right and left of the front end of a vehicle, respectively. A front turn signal lamp or clearance lamp is provided on the outside of each of the headlamps as viewed in the direction of width of the vehicle body, and therefore the headlamps are shifted to wards the central axis of the vehicle body as much. Hence, the lens of the conventional headlamp suffers from the following drawbacks: That is, even if the surface configuration of the lens is curved along the front configuration of the front end portion of the vehicle body; more specifically, even if it is extended outwardly as viewed in the direction of width of the vehicle body and somewhat curved backwardly, their angles of inclination to the right and left are not so large. This may be said about a headlamp with a discharge bulb.
In the above-described headlamp, the straight lines connecting the light emitting section of the discharge bulb to the outermost ends (as viewed in the direction of width of the vehicle body) of the lens surface form sideward open angles with respect to the axial line (in the front-to-rear direction) of the vehicle body. Those sideward open angles are relatively small, and cannot be set to a large value.
Hence, heretofore, although the light beam reflected from the reflector irradiates forwardly of the vehicle, it is impossible to employ a method for effectively utilizing the great power of the discharge lamp to emit a light beam directly from the discharge bulb so as to irradiate sidwardly of the vehicle body thereby allowing the driver to see a shoulder of a road sufficiently.